Pyridoxine dehydrogenase from yeast, an inhibitor of this enzyme also from yeast, and an inducible, membrane-bound 4-pyridoxic acid dehydrogenase from Pseudomonas MA-1 are being purified and characterized. These efforts will continue. In addition, the histidine decarboxylase from Clostridium perfringens (welchii) has been isolated. Its molecular parameters are to be determined, and, in particular, whether it is a pyruvoyl enzyme (as preliminary findings suggest) or a pyridoxal-P enzyme. The inducible pyridoxic acid dehydrogenase may provide an interesting model to study insertion of new proteins into membranes; some study will be directed to this process.